Method and apparatus for the differential detection of combustible atmospheres.



T. M. & E. M CHANCE.

METHOD AND APPARATUS FOR THE DIFFERENTIAL [)FTECIIUN 0F C(WBUSTIBLEATMOSPHERE-S.

APPLICATION FILED MAY i. WIT.

1,298,890., T lutvnl'wi Apr. 1, I919,

WITNESSES: INVENTORS:

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THOMAS M. CHANCE, OF WILKES-BARREL EDWIN M. CHAN CE, OlF PHILADELPHIA,PENNSYLVANIA.

METHOD AND APPARATUS FOR THE DIFFERENTIAL DETECTION OF COMBUSTIIBLEATMOSPHERES.

Patented Apr. 1, 1919.

Application filed May 1, 1917. Serial No. 165,722.

To all whom it may concern:

Be it known that we, THOMAS M. CHANCE and EDWIN M. CHANCE, citizens ofthe United States, and residing, respectively, at \Vilkes-Barre andPhiladelphia, in the State of Pennsylvania, have invented a certain newand Improved Method and Apparatus for the Differential Detection ofCombustible Atmospheres, of which the following is a specification.

The object of our invention is to provide means whereby the presence ofcombustible gases in the atmosphere may be made known provement inmethod and apparatus disin which one comclosed in said application,

detected bustible gas may be differentially with reference to another.

To attain this end We provide a source of heat and an oxidizingmaterial, both of said elements being in operative relation totemperature responsive elements operatively connected to aural or visualsignal devices.

The drawing represents a vertical crosssection illustratingdiagrammatically the general association of elements necessary to theoperation of our invention.

In the drawing 1 indicates a tubularcontainer filled with copper oxid 2,said copper oxid being so arranged in said tube and of such physicalcharacter as to be .readily permeated by the atmosphere to be tested. Athermostatic device, in this case a tube 3 provided with an expansionchamber 4 and electrical contacts 5 and 6 (said tube and .expansionchamber containing mercury 7)' is arranged in operative relatlon to saidcontainer 1 and said copper oxid filling 2. A source of heat 8 isprovided in operative re lation to said container 1 and copper oxidfilling 2, this" source of heat in this case conslsting of a receptacle9 filled with a liquid bath 10, an inlet 11 for the renewal of said bathand a heating coil 12 for maintaining said bath at its boiling point. Ifdesired a discharge 13 may be connected to said container l0,'saiddischarge 13 conducting the vapor evaporated from said bath to asuitable condenser, from whence it may be re turned to inlet 11. Acasing 14 is adapted to inclose the apparatus, said casing being fittedwith an inlet 15 and a discharge 16;

the function of said casing being to provide.

means whereby the atmosphere to be tested may be forced through theapparatus, drawn through by means of an exhauster, or insome casesautomatically caused to flow through said apparatus by the chimneyefi'ect produced by source of heat 8; and also to assist in isolatingsaid apparatus from the exterior.

Electrical contact 5 is connected by means of circuit 17, sourceofelectrical energy 18,

electrically operated alarm 19 and circuit 20 to electrical contact 6,said contact 5 and 6 being adapted to be placed in circuit by therisingof mercury in tube 3. Foraminous means, in this case gauzes 21and 22,may if necessary be provided for preventing propagation. of flame to theexterior atmosphere, and, together with casing 14, completely isolatingthe apparatus from the exterior.

The operation of the apparatus illustrated is as follows: Assuming theapparatus to be operating in normal atmosphere, the copper oxid filling2 will reach its normal temperature and the mercury 7 will become heatedthereby and rise to the level of normal operation indicateddiagrammatically by the line AA. Circuits 17 and 20 will not beenergized as, although contact 5 is covered by the mercury in the lowerportion of tube 3 and expansion chamber 4, said mercury will not rise tothe level of contact 6 under conditions of normal. operation.

If now an atmosphere containing a combustiblegas, such as carbonmonoxid, flow through the apparatus, heat will "be generated bytlieoxidation thereof caused by contact with copper oxid 2, the saidcopper oxid being maintained at a temperature which will cause thereduction of said oxid by carbon monoxid, but not at a high enoughtemperature to cause the combustion of the carbon monoxid, and theoxygen contained in the atmosphere. In other words, the copper oxid actsas a selective oxidizing agent for the oxidation of the carbon monoxid.A

The mercury 7 is now further heated by the heat liberated during thisreaction and expands, rising "in tube 3 until, if the percentage ofcarbon monoxid be high enough to cause the required elevation'intemperature, it makes contact with electric contact 6, closing circuits17 and 20 and operating alarm 19, thus providing a warning .of thepresence of a certain percentage of carbon monoxid.

If hydrogen. be passed through .the apparatus it will operate the devicein approximately the same manner as though carbon monoxid were present,but as these two gases are almost invariably associated in many 10-cations where it is desirable to detect carbon monoxid, such'as in coalmines, the fact that the hydrogen will also operate the apparatus merelyserves to reinforce the carbon monoxid warning, and as the two gases ifsimultaneously present will both assist in the operation of theapparatus, the combustion of the hydrogen will permit the detection ofsmaller quantities of the carbon monoxid than might otherwise be thecase.

It, will of course be-understood that gases:

such as methane may be detected by the use of this apparatus providedthat the oxidizing agent be maintained at a sufiiciently hightemperature to cause the oxidation of the methane. This differentialor'selective ac-' tion of the method is one of the principal objects ofour invention, as it will enable the simultaneous and differentialdetection of different gases, such for example,'as carbon monoxid andhydrogen on the one hand and methane on the other hand.

To accomplish this end it is simply necessary to pass the suspected airthrou h .aplurality of, a paratus of thev types own in the figure, t efirst oxidizing chamber being maintained at a temperature that willoxidize the carbon monoxid and hydrogen but that will not aifect themethane, and the second 4 oxidizing chamber being maintained at atemperature that willoxidize the methane. If it be desired to make afurther diflerentiation, it will be possible to remove the carbonmonoxid or hydrogen by passing it through an oxidizing chambermaintained at a temperature that will oxidize the one but that is toolow to' oxidize the other. It will of course be understood that when aplurality of combustion chambers are used for selectively detectingcombustible gases of different composition, the signaling devicesconnected to the various combustion chambers may be separate so that aseparate signal and apparatus will function in vitiated atmospheres thatwould not support the combustion of these combustible gases, due to thelow oxygen percentage, or even to the absence'of ox gen.

As the maximum temperature that will be I reached by any definiteercentage of the combustible gas is fixed E 1, the heat of combustion ofthe gas, 2, the rate of flow of the gas, or gas and air, through theapparatus and '3, the rate of heat loss of the apparatus as a whole, itwill. be clear that the two latter quantities are possible of controland that all three may be considered as constant for any givenapparatus. Hence it is readily possible to so fix their relation that adefinite predetermined percentage of the gas to be detected will berequired to cause the operation of the thermostatic device and warningsignal. Physical properties of the gas, such as specific heat, etc., maybe con sidered to be approximately constant for the purpose of theoperation of the apparatus.

It will be desirable torestrict the flow of the. air, or gas and air, tobe tested through the apparatus in order to'keep the conditionsconstant, as outlined in the preceding paragraph. It is also necessaryto maintain the oxidizing material at an approximately uniformtemperature, and in certain cases this may be readily attained bypreheating the'air, or gas and air, to' the desired tem-' perature priorto passing it over the oxidizing material. In such' cases it will notalways be necessary to heat extraneously the oxidizing material, as theair to be tested may perform. this function.

.In certain cases a catalytic oxidizing material may be used, as forexample, when hydrogen is to be detected, and under these conditions theinitial rise in temperature of the oxidizing element maybe caused, or

assisted, by catalytic action.

It will be understood that a great variety of devices may be used in theoperation of our method and in the construction of apparatus therefor,and it has not been deemed necessary to illustrate and describe atlength a great number of different types and modifications of suchapparatus. For example, the thermostatic element may be widely varied,as any type of thermostatic device in common use may be employedprovided it possesses the necessary operating characteristics While thedrawing shows an electrical connection between the signaling means andthe thermostatic element, it will of course be understood" that otherdevices may be used therefor.

It will be understood that the invention may be-employed in either astationary or portable form, and that one or more detectors may operateby remote control a single signal or that a plurality of signalingdevices may be operated by one or more detectors. I

In the application for patent dated A ril 14, above referred to, anumber of modi ca tions of apparatus are shown for carrying out thegeneric method of gas detection therein described and claimed, and itwill be understood that many of these modifications may be employed withthe present invention and also that the subject matter described andclaimed herein is subject to the dominating features of the disclosuresin said application for patent.

The operation of our invention is not limited to the use of copper oxidbut depends upon the use of any metal, or metalloid, compound,containing oxygen, which whe maintained at suitable temperature willbause the-desired oxidation of the combustible gas which is to bedetected, and the term oxidizing agent in the claims hereof, is used to.designate such compound.

In the operation of our invention it will of course be understood thatthe oxidizing agent, such as copper oxid, will become reduced by thepassage of the combustible gas through it andv that this oxidizing agentmay either be renewed from time to time or ma be re-oxidized by theaction of a strong y oxidizing atmosphere.

Having described our invention we claim:

1. The method of detecting changes in the constituent gases of theatmosphere which consists in maintaining a'temperature responsiveelement in operative relation to an oxidizing agent and to a source ofheat, said element being operatively connected to signaling means; incausing said element to 0perate said signaling means when thetemperature of said element reaches a predetermined limit; and inpermitting variations in the heat received from said source of heat, dueto the chemical reduction of said oxidizing agent caused by changes insaid constituent gases, to cause the temperature of said element toreach said limit; whereby said signaling means are operated and awarningof said changes given.

2. The method of detecting changes in the constituent gases of theatmosphere which consists in maintaining a temperature responsiveelement in operative relation to an'oxidizing agent and to a source ofheat, said element being electrically connected to signaling means; incausing said element to operate said-signaling means when the oxidizingagent and to a source of heat, said element being operatively connectedto signaling means; in causing said element to operate said signalingmeans when the temperature of said element reaches a predeterminedlimit; and in permitting variations in the heat received from saidsource of heat, due to the chemical reduction of said oxidizing agentcaused by changes in said constituent gases, to cause the temperature ofsaid element to reach said limit; whereby said signaling means areoperated and a warning of said changes given, means being provided forpreventing propagation of flame to the exterior.

4. The method of detecting changes in the constituent gases of theatmosphere which consists in maintaining a temperature responsiveelement in operative relation to an oxidizing agent and to a source ofheat, said element being electrically connected to signaling means; incausing said element to operate said signaling means when thetemperature of said element reaches a predeter mined limit; and inpermitting variations in the heat received from said source of heat, dueto the chemical reductionof said oxi dizing agent caused by changes insaidconstituent gases, to cause the temperature of said element to'reach said limit; whereby said signaling means are operated and awarning of said changes given, means bein provided for preventingpropagation o 6. Apparatus for the detection of changes in theconstituent gases of theatmosphere, comprising in combination anoxidizing agent, a source ofheat in operative relation thereto, atemperature responsive element in operative relation to said agent, andelectrical signaling means operatively connected to said temperatureresponsive element.

In testimony whereof THOMAS M. CHANGE has signed his name atPhiladelphia, Pennsylvania, the 28th day of April, 1917, and

VEDWIN M. CHANGE has signed his name at Wilkes-Barre, Pennsylvania, the30th day of April, 1917.

THOMAS M. CHANCE. EDWIN M. CHANCE. Witnesses as to Thomas M. Chance:

H. M. CHANCE, CARL K. SoHULzE. Witnesses as to Edwin M. Chance:

G. W. REYNOLDS, JOSEPH FLUEGEL.

